RavenDB升级：2.5到3.5 - 无法编译索引

我目前正在将我们的解决方案从RavenDB 2.5升级到3.5但在创建索引时遇到以下异常：看起来它与 group by 有关

IndexCreation.CreateIndexes(typeof(RavenGuid).Assembly, store);

Index Definition

public RecordingArtistTypeaheadIndex()
{
    Map = docs => docs.Select(x => new Definition { Artist = x.ArtistDisplayName });

    Reduce = results => results.SelectMany(r => r.Artist.Split('|')).GroupBy(x => x).Select(g => new Definition { Artist = g.Key });

    Store(x => x.Artist, FieldStorage.Yes);

    Index(x => x.Artist, FieldIndexing.Analyzed);
}

Exception message

Compilation Errors:

Line 40, Position 11: Error CS1525 - Invalid expression term 'by'
Line 40, Position 14: Error CS0745 - Expected contextual keyword 'by'

Source code

public class Index_RecordingArtistTypeaheadIndex : Raven.Database.Linq.AbstractViewGenerator
{
    public Index_RecordingArtistTypeaheadIndex()
    {
        this.ViewText = @"from x in docs.RepertoireResources
                          select new {
                              Artist = x.ArtistDisplayName
                          }
                          from x in results.SelectMany(r => r.Artist.Split(new char[] {'|'}))
                          group x by x into g
                          select new {
                              Artist = g.Key
                          }";

        this.ForEntityNames.Add("RepertoireResources");

        this.AddMapDefinition(docs => 
            from x in ((IEnumerable<dynamic>)docs)
            where string.Equals(x["@metadata"]["Raven-Entity-Name"], "RepertoireResources", System.StringComparison.InvariantCultureIgnoreCase)
            select new {
                Artist = x.ArtistDisplayName,
                __document_id = x.__document_id
            });

        this.ReduceDefinition = results => 
            from x in results.SelectMany((Func<dynamic, IEnumerable<dynamic>>)(r => (IEnumerable<dynamic>)(r.Artist.Split(new char[] {
                '|'
            }))))
            group  by x into g
            select new {
                Artist = g.Key
            };

        this.GroupByExtraction = x => x;
        this.AddField("Artist");
        this.AddQueryParameterForMap("ArtistDisplayName");
        this.AddQueryParameterForMap("__document_id");
        this.AddQueryParameterForReduce("ArtistDisplayName");
        this.AddQueryParameterForReduce("__document_id");
    }
}

以前有人遇到过这个吗？